The eastern metropolis continued to be swamped by rains triggered by a massive depression on the Bay of Bengal over the last three days.

The deluge in Kolkata and the adjoining districts claimed 12 lives as boats sailed through the flooded city, ferrying people and reaching succour to those affected in many areas.

"All affected districts have been alerted in view of the situation and we are reaching succour," West Bengal Relief Minister Mortaja Hossain said on Thursday.

Meanwhile, government health workers and volunteers were distributing medicines and disinfectants to prevent epidemic.

Meteorological department regional director G C Debnath said more rains were expected as the south Bengal districts of Hooghly, Bankura, Birbhum and Midnapore East and West experienced torrential rains.

"It will continue to rain since a low pressure over the Bay of Bengal has developed into depression and is hovering over Bangladesh. The depression lies 50 km north of Kolkata," Debnath explained. The depression earlier lay 150 km South-East of Kolkata.

The meteorological office said 110.3 mm rainfall was recorded in Kolkata's Dum Dum area in the past 24 hours.

Since Tuesday, boats were being used to supply dry food and drinking water in large parts of north Kolkata, especially in Amherst Steet and Sukia Street areas. There was no electricity in several parts of the city.

Train services to and from Kolkata were seriously affected for the third day on Thursday, but flights were on schedule. Several local and long distance trains were either cancelled or rescheduled, railway sources said.

Bus services were also disrupted in Kolkata while cars got stranded at several areas. The underground Metro rail services were the only saving grace.

Meanwhile, resentment against the Left Front-ruled Kolkata Municipal Corporation had been mounting and people were calling up television channels to vent their ire.

Most people blamed Mayor Bikash Ranjan Bhattacharya for not having done enough before the monsoon began to mitigate water logging problems. The mayor was even surrounded for a while by the opposition Trinamool Congress councillors.

"There is water-logging but our pumps worked to drain out the water. We tried our best to pump out water. You have to understand that our measures to improve the civic amenities would yield result in time," the mayor pleaded.

Schools and colleges remained closed and all University exams have been deferred.